Reconnection Rate in the Decay Phase of a Long Duration Event Flare on 1997 May 12
Reconnection Rate in the Decay Phase of a Long Duration Event Flare on 1997 May 12
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DOI：
10.1086/324777
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发表时间：
2002-02
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影响因子：
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通讯作者：
H. Isobe;T. Yokoyama;M. Shimojo;T. Morimoto;H. Kozu;Shigeru Eto;N. Narukage;K. Shibata
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文献类型：
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作者：
H. Isobe;T. Yokoyama;M. Shimojo;T. Morimoto;H. Kozu;Shigeru Eto;N. Narukage;K. Shibata
最近对长持续时间事件（LDE）耀斑的分析表明，在衰变阶段连续发生磁重联和由此产生的能量释放。然而，目前尚未对能量释放率和重联率进行定量研究。在本文中，我们关注 1997 年 5 月 12 日 LDE 耀斑的衰变阶段，并推导出能量释放速率 H 和重联速率 MA = vin/vA，其中 vin 是流入速度，vA 是阿尔文速度。为此，我们利用以下关系间接确定 vin 和日冕磁场 Bcorona：其中 Ar、Bfoot 和 vfoot 分别是重联区域的面积、足点处的磁场强度和足点的分离速度。由于 H、Ar、vfoot 和 Bfoot 是从 Yohkoh 软 X 射线望远镜数据和光球磁图获得的，因此可以根据这些方程确定 vin 和 Bcorona。结果如下： 衰变阶段的 H 约为 1027 ergs-1。该值大于上升阶段值的 1/10。 MA 为 0.001-0.01，比之前的研究结果小约 1 个数量级。然而，在非统一填充因子的合理假设下，它可以与之前的研究保持一致。 Bcorona 被发现在 5-9 G 范围内，这与野边山射电日光仪观察到的电势外推和微波偏振一致。
Recent analyses of long duration event (LDE) flares indicate successive occurrences of magnetic reconnection and resultant energy release in the decay phase. However, quantitative studies of the energy release rate and the reconnection rate have not yet been made. In this paper we focus on the decay phase of an LDE flare on 1997 May 12 and derive the energy release rate H and the reconnection rate MA = vin/vA, where vin is the inflow velocity and vA is the Alfvén velocity. For this purpose, we utilize a method to determine vin and the coronal magnetic field Bcorona indirectly, using the following relations: where Ar, Bfoot, and vfoot are the area of the reconnection region, the magnetic field strength at the footpoints, and the separation velocity of the footpoints, respectively. Since H, Ar, vfoot, and Bfoot are obtained from the Yohkoh Soft X-Ray Telescope data and a photospheric magnetogram, vin and Bcorona can be determined from these equations. The results are as follows: H is ~1027 ergs s-1 in the decay phase. This is greater than 1/10th of the value found in the rise phase. MA is 0.001-0.01, which is about 1 order of magnitude smaller than found in previous studies. However, it can be made consistent with the previous studies under the reasonable assumption of a nonunity filling factor. Bcorona is found to be in the range of 5-9 G, which is consistent with both the potential extrapolation and microwave polarization observed with the Nobeyama Radioheliograph.